Rocktron Xpression - Manual (Page 25)

Functions and Parameter Descriptions
The HUSH ® function is accessible in all presets—regardless of the con-
figuration currently recalled.
HUSH is Rocktron’s patented single-ended noise reduction system. The
HUSH system contained in the Xpression is a fully digital implementation of
HUSH achieved through Digital Signal Processing (DSP), and is modeled after
the latest HUSH design.
The low level expander of the HUSH system operates like an electronic
volume control. The analog version of the HUSH utilizes a voltage-controlled
amplifier (VCA) circuit which can control the gain between the input and the
output from unity to 30, 40 or even 50dB of gain reduction. When the input
signal is above the user preset threshold point, the VCA circuit remains at unity
gain. (This means that the amplitude of the output signal will be equal to that of
the input signal.) As the input signal level drops below the user preset threshold
point, downward expansion begins. At this point the expander acts like an
electronic volume control and gradually begins to decrease the output signal
level relative to the input signal level. As the input signal drops further below
the threshold point, downward expansion increases. A drop in the input level by
20dB would cause the output level to drop approximately 40dB (i.e., 20dB of
gain reduction). In the absence of any input signal, the expander will reduce the
gain so that the noise floor becomes inaudible.
The HUSH circuit is located after the A/D converter in the signal chain to
reduce any noise generated from the guitar, any guitar preamp and the A/D
converter. This ensures a quiet input signal to the Xpression effects.
When the DRY PATH parameter under the Mixer function is set to "DIGI-
TAL", the direct signal is passed through the HUSH circuit. When set to "ANA-
LOG", the direct signal remains analog and does not pass through the HUSH
circuit.
The PARAMETER SELECT control will allow you to access each of the following
Hush parameters.
The PARAMETER ADJUST control will allow you to make adjustments to the
parameter selected:
HUSH
Function
HUSH I/O
EXP THRESH
The HUSH I/O parameter determines whether the HUSH circuit is
active or bypassed for the current preset.
Select IN and the HUSH is active.
Select OUT and the HUSH is bypassed.
The EXPANDER THRESHOLD parameter determines the level at
which downward expansion begins. For example, if the EXPANDER
THRESHOLD was set at -27dB and the input signal dropped below
-27dB, downward expansion would begin. The will be more noise
reduction at higher settings. If you are using a very noisy, hi gain
preamp higher settings like -27 will provide the most noise reduction.
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